Automotive window regulators are required to resist backdrive in order to prevent a partially opened window from being forced down from the outside of the vehicle, such as in a break-in attempt. Current industry practice is to resist backdrive by using a torsion spring clutch in a manual window regulator, and by the electric motor gear ratio in a power window regulator. The disadvantages of both these systems is that the complete window regulator must be robust enough to withstand the backdrive force since the transmitted load path extends all the way from the window glass to the lift plate to the drive assembly (either a manual crank assembly or a power motor). In addition, the traditional methods of resisting backdrive create inefficiencies when the window regulator is operated normally. In a manual system the clutch torque, which could be as
high as 20% of the total operating torque, must be overcome before motion is transmitted to the lift plate. In a power system, single-start worms are required in the motor gearset to ensure suitable backdrive gear efficiency, but single-start worms also create a very low driving efficiency for normal operation of the window regulator.
It is therefore desired to provide a window regulator that resists backdrive in a manner that mitigates or obviates at least one of the above-described disadvantages.